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Contraherent cosheaves are globalizations of contraadjusted or cotorsion modules over commutative rings obtained by gluing together over a scheme, with the colocalization functors $\operatorname{Hom}_R(S,{-})$ used for the gluing (where $S$…

Category Theory · Mathematics 2025-12-03 Leonid Positselski

The category of coherent sheaves over a noetherian scheme is very important for studying the properties of a given scheme. For noetherian schemes it is a well-known fact that the topology can be fully recovered from the corresponding…

Algebraic Geometry · Mathematics 2025-07-08 Ron Held

We show that, for a Noetherian algebraic stack with quasi-affine diagonal $X$, the stable $\infty$-category of quasi-coherent sheaves on $X$ is dualizable if and only if the reduced identity component of the stabilizer of $X$ at every…

Algebraic Geometry · Mathematics 2025-09-18 Germán Stefanich

We prove an analogon of the the fundamental homomorphism theorem for certain classes of exact and essentially surjective functors of Abelian categories $\mathscr{Q}:\mathcal{A} \to \mathcal{B}$. It states that $\mathscr{Q}$ is up to…

Category Theory · Mathematics 2016-12-06 Mohamed Barakat , Markus Lange-Hegermann

The notion of a duality between two derived functors as well as an extension theorem for derived functors to larger categories in which they need not be defined is introduced. These ideas are then applied to extend and study the coext…

Rings and Algebras · Mathematics 2014-02-19 Anastasis Kratsios

There are two dual equivalences between the $\infty$-category of $\mathcal{O}$-monoidal $\infty$-categories with right adjoint lax $\mathcal{O}$-monoidal functors and that with left adjoint oplax $\mathcal{O}$-monoidal functors, where…

Category Theory · Mathematics 2025-01-28 Takeshi Torii

We arrange morphisms and comorphisms of sites as the horizontal and vertical cells of a double category of sites; using the formalism of extensions and restrictions of presheaves, we explains how one can define a sheafification double…

Category Theory · Mathematics 2025-05-14 Olivia Caramello , Axel Osmond

Continuation of algebraic structures in families of dynamical systems is described using category theory, sheaves, and lattice algebras. Well-known concepts in dynamics, such as attractors or invariant sets, are formulated as functors on…

Dynamical Systems · Mathematics 2022-07-14 K. Dowling , W. D. Kalies , R. C. A. M. Vandervorst

We show that certain categories of perverse sheaves on a pair of affine toric varieties defined by dual cones are Koszul dual in the sense of Beilinson, Ginzburg and Soergel. The functor expressing this duality is constructed explicitly…

Algebraic Geometry · Mathematics 2007-05-23 Tom Braden

We describe an analogue of the notion of a perverse sheaf in the setting of the derived category of coherent sheaves on an algebraic stack. Under strong additional assumptions the construction of coherent "intersection cohomology" complexes…

Algebraic Geometry · Mathematics 2021-02-04 Dmitry Arinkin , Roman Bezrukavnikov

In this short note we prove that two definitions of (co)ends in $\infty$-categories, via twisted arrow $\infty$-categories and via $\infty$-categories of simplices, are equivalent. We also show that weighted (co)limits, which can be defined…

Category Theory · Mathematics 2021-03-09 Rune Haugseng

This paper is the first in a series of papers in which we define and study a category of "sheaves of $\mathcal Z$-modules on the set of alcoves" that carries important information on the category of representations of semisimple Lie…

Representation Theory · Mathematics 2017-01-16 Peter Fiebig , Martina Lanini

We develop a general theory of extensions of flat functors along geometric morphisms of toposes, and apply it to the study of the class of theories whose classifying topos is equivalent to a presheaf topos. As a result, we obtain a…

Category Theory · Mathematics 2014-06-23 Olivia Caramello

Motivated by problems in which data are given over covering generating families, we suggest a new cohomology theory for diffeological spaces, called diffeological \v{C}ech cohomology, which is an exact $ \partial $-functor of the section…

Differential Geometry · Mathematics 2023-03-07 Alireza Ahmadi

We develop a homotopy theory for additive categories endowed with endofunctors, analogous to the concept of a model structure. We use it to construct the homotopy theory of a Hovey triple (which consists of two compatible complete cotorsion…

Representation Theory · Mathematics 2017-03-09 Zhi-Wei Li

Consider a complete abelian category which has an injective cogenerator. If its derived category is left--complete we show that the dual of this derived category satisfies Brown representability. In particular this is true for the derived…

Category Theory · Mathematics 2016-06-28 George Ciprian Modoi

In two articles by Barthel, Brasselet, Fieseler and Kaup, and, Bressler and Lunts, a combinatorial theory of intersection cohomology and perverse sheaves has been developed on fans. In the first one, one tried to present everything on an…

Algebraic Geometry · Mathematics 2007-05-23 Karl-Heinz Fieseler

This paper develops a theory of colimit sketches "with constructions" in higher category theory, formalising the input to the ubiquitous procedure of adjoining specified "constructible" colimits to a category such that specified "relation"…

Category Theory · Mathematics 2021-11-25 Andrew W. Macpherson

We introduce a notion of Poincar\'e duality for pairs of $\infty$-categories, extending Poincar\'e-Lefschetz duality for pairs of spaces. This categorical extension yields an efficient book-keeping device that affords, among other things, a…

Algebraic Topology · Mathematics 2025-10-24 Andrea Bianchi , Kaif Hilman , Dominik Kirstein , Christian Kremer

The Dowker complex is an abstract simplicial complex that is constructed from a binary relation in a straightforward way. Although there are two ways to perform this construction -- vertices for the complex are either the rows or the…

Algebraic Topology · Mathematics 2020-05-27 Michael Robinson